This is related to: Request - internal call and SMS blocklist
The ability to select an option to block calls on rejection or after the call has ended would be very useful. The plus the ability to edit the list manually in Settings, or the Phone Settings. These days with spam calls and re-used numbers, it’s beconing more of a must have, than a nice to have.
I currently use the Phone Hook application for this functionality, and while it’s done as well as can be managed as an app, builidng the functionality into the OS would be a lot neater, especially, it’s often required to uninstall it before upgrades.